280 HISTOLOGY OF THE MORBID PROCESSES. 



8. Hyaline Degeneration. This term is used to designate the 

 occurrence of a material similar to colloid, which appears chiefly in 

 the intercellular substances or in the interstices of the tissues, and is 

 apparently not immediately derived from the substance of cells. It 

 is a question whether it should, in such cases, be regarded as a 

 degeneration i. e. 9 the result of a transformation of pre-existent 

 normal structures or whether it is not a form of infiltration, the 

 material being simply deposited between the normal structures, 

 which may atrophy and disappear in consequence of its presence. 

 Its most common site is beneath the endothelial linings of the 

 bloodvessels, where it forms a homogeneous layer, greatly thicken- 

 ing the vascular wall and often causing a narrowing of the lumen 

 of the vessel (Figs. 251 and 252). It may also affect the fibrous 

 tissues, replacing the intercellular substances with hyaline material, 

 made up of an agglomeration of little masses, or appearing quite 

 homogeneous. The cells of the tissues gradually undergo atrophy 

 and disappear, but do not seem in most cases to suffer a transforma- 

 tion into hyaline substance. In some instances, however, the cyto- 

 plasm of the cells appears to undergo a hyaline transformation 

 (Fig. 251). 



A hyaline transformation sometimes affects thrombi, which lose 

 their fibrinous character and become homogeneous. 



Hyaline material may take a faint bluish tint when treated with 

 hsematoxylin, or it may remain colorless. 



Various attempts have been made to define more clearly the con- 

 ceptions of colloid and hyaline substances, and to distinguish them 

 by means of reactions with different staining-fluids. These attempts 

 have not led to satisfactory results, probably because the colloid 

 and hyaline substances are mixtures of various chemical compounds ; 

 the whole subject awaits further investigation. 



9. Keratoid Degeneration. This form of degeneration is a trans- 

 formation of the cytoplasm into a substance called keratin, which 

 gives to horn, the nails, etc., their peculiar character. It is nor- 

 mally produced in the epidermis, where this degenerative process is 

 not pathological. The transformation appears to involve the pre- 

 liminary formation of a substance called eleidin (Fig. 175), the 

 chemical nature of which is unknown, which subsequently changes 

 into keratin. These two substances may be distinguished by the 

 facts that eleidin is deeply stained by carmine and not by fuchsin, 

 while keratin is readily stained by the latter dye. 



